I found the following information in the document's footer (last few lines on each page):
- Date: December 2011
- Title: "I-5 to Medina: Bridge Replacement and HOV Project
Final Wetland Mitigation Report"
- Type of Document: Report
Googling this information yields the author, namely the Washington State Department of Transportation, SR 520 Bridge Replacement and HOV Program, and the location, which is Seattle, WA. In this case, the author is also the publisher (although I would omit the part after the comma).
I leave it to you as an exercise to compile this information into an APA citation.